In general, the discovery of “whispering gallery (WG)” effect by Lord Rayleigh (see, ‘philosophical magazine’, vol. XX. pp. 1001-1004, 1910) has led to active researches upon the amplification of sound waves, microwaves, and light waves. Among the various researches, a thumbtack-type WG laser developed by Bell Laboratories has attracted considerable attention (see, “Whispering gallery mode micro-disk lasers”, A, F, J, Levi, R. E. Slusher et al, Appl. Phys. Lett. 60.289, 1992). However, the thumbtack-type WG laser is two-dimensional, and it exhibits such a drawback of poor durability and accompanies several problems such as an output coupling and electro-pumping, which result in a difficulty of the manufacture thereof.
In order to solve the problems, a photonic quantum ring (PQR) laser has been proposed by Applicants (see, J. C. Ahn et al., “Photonic Quantum Ring”, Phys. Rev. Lett. Vol. 82(3), pp. 536-539, January 1999; and U.S. Pat. No. 6,519,271 B2 and its counterpart Japanese Patent No. 3,333,747, which is commonly assigned to one of applicants, POSTECH foundation and is incorporated herein by reference.
The PQR laser has a configuration of three-dimensional cylindrical mesa similar to that of a vertical cavity surface emitting laser (VCSEL) of an electrical pumping type, and oscillates in a WG mode, thus effectively solving the problems of the poor device durability and the output coupling. Based on the hypothesis of a photonic quantum corral effect (PQCE) (analogous to the following: Y. Hasegawa and Ph. Avouris, “Direct observation of standing wave formation at surface steps using scanning tunneling spectroscopy”, Phys. Rev. Lett. 71, pp. 1071, 1993; M. F. Crommie et al, “Imaging standing waves in a Two-dimensional electron gas”, Nature, 363, pp. 524, 1993; C. Chicanne et al, “Imaging the local density of states of optical corrals”, Phys. Rev. Lett. 88, pp. 97402, 2002), characteristics of threshold current of the PQR laser ranging from nA to μA can be explained (B. H. Park et al, “Chiral wave propagation manifold of the photonic quantum ring laser”, Appl. Phys. Lett. Vol. 81, pp. 580-582, July 2002, E. Gehrig et al, “Dynamic filamentation and beam quality of quantum-dot lasers”, Appl. Phys. Lett. 84, pp. 1650, 2004).
The thumbtack-type 2D-WG laser and the cylindrical mesa structured 3D-WG PQR laser are all based on the total reflection generated inside a resonator having concave surfaces, as described in the principle of Rayleigh's concavity which has been employed since 1912.
Further, a flatness process is additionally needed to fabricate the thumbtack-type 2D-WG laser and the cylindrical mesa structured 3D-WG PQR laser by using a polyimide in order to endow them the electro-pumping capability.